Influence of fiber orientation on the ballistic performance of needlepunched nonwoven fabrics

Abstract

a b s t r a c tThe influence of the initial fiber orientation distribution on the ballistic performance of a needlepunched nonwoven polyethylene fabric was analyzed. To this end, ballistic tests were carried out in specimens pre-deformed along the machine or the transverse directions and the influence of pre-deformation on the fiber orientation was measured by means of wide angle X-ray diffraction. It was found that pre-deformation along the machine direction (the soft orientation of the fabric) led to more isotropic in-plane mechanical response and to a marked increase in the specific ballistic limit and in the energy dissipated by unit weight while the opposite behavior was found after stretching the fabric along the transverse direction. These differences were accompanied by changes in the penetration mechanics from extensive fiber pull-out to slippage between fibers in the network. These results highlight how the nature of the nonwoven microstructure (connectivity of the entanglement points and fiber orientation distribution) can be tailored to improve the impact performance.

Dynamic Tensile Testing of Needle-Punched Nonwoven Fabrics

“…The manufacturing process introduced two orthogonal principal material orientations denominated the roll or machine (MD) and transverse (TD) directions, inducing a higher fibre connectivity along the TD with larger volume fraction of entangled active fibres. The quasi-static in-plane tensile response and the ballistic performance of the material have been previously characterised, and the main deformation and failure mechanisms are briefly recalled in Section 4.1 for the sake of completion [15,19,44].…”

“…Although the model captured the ballistic limit and the failure mechanisms for different fibre ODFs, it overestimated the energy absorption above the penetration threshold as a result of inaccuracies when modelling the wave propagation phenomenon. Further details are available in [19,21].…”

“…As a result, the samples with gauge length lower than 30 mm possessed a higher strength and stiffness and presented a significant percentage of fibre breakage, identified by a rough stress-strain curve at the onset of damage, as opposed to the representative smooth baseline mechanical response. The tensile fibre breakage was not a dominant failure mode of needle-punched nonwoven fabrics subjected to in-plane tensile loads or ballistic impact [15,19], nevertheless, the influence of this mechanisms could be neglected for gauge dimensions larger than half the average fibre length (30 mm).…”

“…It is possible to find in the literature multiple applications for protective barriers based on nonwoven fabrics for soft body armour and the transport industry [5][6][7][8][9][10]; nevertheless, the biggest improvement in ballistic performance is obtained when nonwoven fabrics are combined with traditional barriers based on dry woven fabrics, as cushion layers, or metal plates with a negligible increment of the total areal weight of the target [4,[11][12][13]. It is possible to find detailed studies focused on the quasi-static response [14,15] and the ballistic performance of the material [10,[16][17][18][19]; nevertheless, there is still a lack of knowledge regarding the effect of high strain rates in its mechanical properties. For instance, a detailed dynamic characterisation is required to understand the differences in the wave propagation (scattering and dissipation) between a continuous medium and the actual network structure [20].…”

A new kind of resin-based wet friction material: Non-woven fabrics with isotropic fiber networks as preforms

“…NWFs are fabric-like material made of relatively long fibers that is prepared by chemical, mechanical, heat treatment or in combination with solvent treatment [9,10]. In the process of NWF production, fibers are loosely distributed, overlapped, and stitched, forming a randomly distributed structural layer with a welldefined pore structure and a large porosity [11].…”